Methods and systems for estimating a composition of flow through a scavenge exhaust gas recirculation system of a split exhaust engine system

Abstract

Methods and systems are provided for controlling operating of a split exhaust engine system including a scavenge exhaust gas recirculation system based on a composition of constituents within a total flow through the scavenge exhaust gas recirculation system. In one example, a method may include adjusting an engine operating parameter in response to individual flows of each of burnt gases, fresh air, and fuel to an intake passage, upstream of a compressor, from a scavenge manifold coupled to scavenge exhaust valves, the individual flows of each of the burnt gases, fresh air, and fuel determined based on a valve opening overlap between the scavenge exhaust valves and intake valves of the engine.

The invention claimed is: 
     
       1. A method for an engine, comprising:
 adjusting an engine operating parameter in response to individual flows of each of burnt gases, fresh air, and fuel to an intake passage, upstream of a compressor, from a scavenge manifold coupled to scavenge exhaust valves, and 
 determining the individual flows of each of the burnt gases, the fresh air, and the fuel based on a valve opening overlap between the scavenge exhaust valves and intake valves of the engine. 
 
     
     
       2. The method of  claim 1 , further comprising opening the scavenge exhaust valves at a different time than blowdown exhaust valves coupled to a blowdown manifold coupled to an exhaust passage including a turbine. 
     
     
       3. The method of  claim 1 , wherein the individual flows of each of the burnt gases, the fresh air, and the fuel are further determined based on total bulk flow to the intake passage from the scavenge manifold, the total bulk flow determined based on a valve opening overlap area between the scavenge exhaust valves and the intake valves and a pressure in each of an intake manifold and the scavenge manifold, where the individual flows of each of the burnt gases, the fresh air, and the fuel add up to the total bulk flow. 
     
     
       4. The method of  claim 3 , wherein the valve opening overlap area is determined based on a first valve lift of the scavenge exhaust valves and a second valve lift of the intake valves, and wherein the valve opening overlap area is an amount of valve opening overlap. 
     
     
       5. The method of  claim 1 , wherein adjusting the engine operating parameter in response to the individual flows of each of the burnt gases, the fresh air, and the fuel includes adjusting a first engine operating parameter in response to the individual flow of the burnt gases, a second engine operating parameter in response to the individual flow of the fresh air, and a third engine operating parameter in response to the individual flow of the fuel. 
     
     
       6. The method of  claim 1 , wherein the adjusting the engine operating parameter in response to the individual flows of each of the burnt gases, the fresh air, and the fuel includes adjusting one or more of a position of a valve disposed in a passage coupled between the scavenge manifold and the intake passage, upstream of the compressor, and an exhaust cam timing in response to the determined individual flow of the burnt gases and based on a desired flow of burnt gases to the intake passage. 
     
     
       7. The method of  claim 1 , wherein the adjusting the engine operating parameter in response to the individual flows of each of the burnt gases, the fresh air, and the fuel includes adjusting one or more of a position of a valve disposed in a passage coupled between the scavenge manifold and the intake passage, upstream of the compressor, an exhaust cam timing, and an intake cam timing in response to the determined individual flow of the fresh air and based on a desired flow of fresh blowthrough air to the intake passage. 
     
     
       8. The method of  claim 1 , wherein the adjusting the engine operating parameter in response to the individual flows of each of the burnt gases, the fresh air, and the fuel includes adjusting one or more of a fuel injection timing and a fuel injection amount in response to the determined individual flow of the fuel and a desired flow of fuel to the intake passage. 
     
     
       9. A method for an engine, comprising:
 determining concentrations of each of burnt gases, fresh air, and unburned hydrocarbons in a total flow of gases to an intake passage, upstream of a compressor, from a scavenge exhaust manifold coupled to scavenge exhaust valves based on an amount of valve opening overlap between the scavenge exhaust valves and intake valves of the engine; and 
 adjusting engine operation based on the determined concentrations. 
 
     
     
       10. The method of  claim 9 , further comprising opening the scavenge exhaust valves at a different time than blowdown exhaust valves coupled to a blowdown manifold coupled to an exhaust passage including a turbine. 
     
     
       11. The method of  claim 9 , wherein the determining the concentrations of each of the burnt gases, the fresh air, and the unburned hydrocarbons includes determining a higher concentration of the burnt gases as the amount of valve opening overlap decreases and wherein the adjusting engine operation includes adjusting one or more of a position of a valve disposed in a passage coupled between the scavenge exhaust manifold and the intake passage, upstream of the compressor, and an exhaust cam timing in response to the determined concentration of the burnt gases being different than a desired flow of burnt gases to the intake passage. 
     
     
       12. The method of  claim 9 , wherein the determining the concentrations of each of the burnt gases, the fresh air, and the unburned hydrocarbons includes determining a higher concentration of the fresh air as the amount of valve opening overlap increases and wherein the adjusting engine operation includes adjusting one or more of a position of a valve disposed in a passage coupled between the scavenge exhaust manifold and the intake passage, upstream of the compressor, an exhaust cam timing, and an intake cam timing in response to the determined concentration of the burnt gases being different than a desired flow of fresh blowthrough air to the intake passage. 
     
     
       13. The method of  claim 9 , further comprising determining a total flow of burnt gases, a total flow of fresh air, and a total flow of unburned hydrocarbons to the intake passage, upstream of the compressor, from the scavenge exhaust manifold based on a total flow of gases and the determined concentrations of each of the burnt gases, the fresh air, and the unburned hydrocarbons, the total flow of gases determined based on a valve opening overlap area between the scavenge exhaust valves and the intake valves, an intake manifold pressure, and a scavenge exhaust manifold pressure. 
     
     
       14. The method of  claim 13 , wherein the valve opening overlap area is based on a valve lift of the scavenge exhaust valves and a valve lift of the intake valves at a current crank angle. 
     
     
       15. The method of  claim 13 , further comprising advancing an exhaust cam timing in response to the determined total flow of burnt gases being lower than a desired flow of recirculated burnt gases to the intake passage. 
     
     
       16. The method of  claim 13 , further comprising retarding an exhaust cam timing in response to the determined total flow of fresh air being lower than a desired flow of recirculated fresh air to the intake passage. 
     
     
       17. The method of  claim 13 , further comprising advancing an intake cam timing in response to the determined total flow of fresh air being lower than a desired flow of recirculated fresh air to the intake passage. 
     
     
       18. A system for an engine, comprising:
 a plurality of cylinders, each including an intake valve, a scavenge exhaust valve, and a blowdown exhaust valve; 
 an intake manifold coupled to the intake valve of each of the cylinders; 
 a scavenge manifold coupled to the scavenge exhaust valve of each of the cylinders and an intake passage, upstream of a compressor, via a scavenge exhaust gas recirculation passage; 
 a blowdown manifold coupled to the blowdown exhaust valve of each of the cylinders and an exhaust passage including a turbine; and 
 a controller with computer readable instructions stored on non-transitory memory that when executed during engine operation, cause the controller to:
 determine a total flow of gases through the scavenge exhaust gas recirculation passage, from the scavenge manifold to the intake manifold, upstream of the compressor, based on a valve opening overlap area between the scavenge exhaust valve and the intake valve; 
 determine a total flow of burnt gases, a total flow of fresh air, and a total flow of fuel through the scavenge exhaust gas recirculation passage based on the determined total flow of gases and an amount of valve opening overlap between the scavenge exhaust valve and the intake valve; and 
 adjust an operating parameter of the engine based on the determined total flow of burnt gases, the determined total flow of fresh air, and the determined total flow of fuel. 
 
 
     
     
       19. The system of  claim 18 , wherein the total flow of burnt gases, the total flow of fresh air, and the total flow of fuel add up to the total flow of gases, and wherein adjusting the operating parameter of the engine includes adjusting one or more of a timing of the intake valve, a timing of the scavenge exhaust valve, and a position of a valve disposed in the scavenge exhaust gas recirculation passage. 
     
     
       20. The system of  claim 18 , wherein the total flow of gases is further determined based on a measured pressure in the intake manifold and a measured pressure in the scavenge manifold.